What Scientists Hope to Learn from Cassini's Dive into Enceladus's Icy Geysers

NASA's Cassini spacecraft took the plunge into the icy geysers of Saturn's moon Enceladus in a close flyby earlier this week, and the mission could be instrumental to discovering extraterrestrial life. The results haven't come in yet (although they're expected to be announced any day now), but scientists are hoping to use the data from the mission to finally evaluate the moon's potential for habitability.

Enceladus is frozen solid, completely covered in ice, and yet it has long been considered to be a prime candidate for extraterrestrial life. The moon has plumes of water vapor venting from the south pole, which led researchers to conclude that they originate in a subsurface ocean. This ocean could be a prime breeding ground for microbes and other forms of life, but this is the first time it's truly been investigated.

Earlier this week, Cassini flew through the water vapor at the south pole, exposing its instruments to the water from the subsurface ocean. The encounter lasted for less than a minute, as the spacecraft was moving at 19,000 miles per hour, but it was still able to sample 10,000 particles that may tell us whether the ocean holds alien life.

"Cassini's instruments do not have the capability to detect life itself," Cassini project scientist Linda Spilker, told Astrobiology Magazine. "Those instruments can, however, make powerful measurements about the ocean and its potential habitability."

First, Cassini is able to detect complex molecules, which could be the result of biological processes. Its instruments would not be able to definitively determine that the molecules were organic, but the detection of these molecules would still be a step in the right direction.

"Cassini has instruments that are capable of detecting complex organic molecules which could possibly be fragments of even larger molecules," said Earl Maize, Cassini's deputy program manager. "However, the instruments are not capable of determining whether the processes are biological or geological."

Second, Cassini may be able to discover the source of the geysers, which could point to the presence of extraterrestrial life. There is an intense heat source that must be causing the ice to melt at the south pole, leading to the subsurface ocean and the water plumes. The scientists believe that the most likely option is tidal heating caused by Enceladus's interaction with Saturn and other nearby moons, but there's also a chance that it could derive from biological activity on the ocean floor.

"I would be very excited to see a detection of a large amount of molecular hydrogen coming from the Enceladus plume," said Spiiker. "This would indicate that a great deal of hydrothermal activity is occurring on Enceladus' seafloor, making it that much more likely that a habitat for life exists in Enceladus' ocean."

However, even if a source of heat is discovered on the ocean floor, that's still a far cry from proof of life. More likely, Cassini would tell us whether the moon is habitable, and whether we should continue to search for alien life in its ocean:

"It's a huge step to go from that to even suggesting that you see signs of life," said Curt Niebur, program scientist for the Cassini mission. "Detecting life is very nuanced and extremely difficult. Which is why, before investing an incredible amount of time, money and mission to do a life-detection, we answer a simple question -is it habitable? Is life even remotely possible? And that's fairly straightforward to assess. That's what Cassini can do."